Most of us have found that when we receive 12-marker results from FamilyTreeDNA, there is a long list of surnames which may or may not include our own name. Test results from this entry level kit have two sets of results — either a 12/12 match or a 11/12 match. Anything beyond a genetic distance of one (1) is considered to be statistically insignificant for genealogical research.
For example, if you have a perfect match (12/12)with another person, you have 81% chance of a common ancestor within the past 16 generations (about 400 years). If the match is an 11/12, then the chances of a common ancestor is 64% within 24 generation (about 600 years). These results suggest a common ancestor during the time when surnames were very uncommon, so any surname matches are few and require very strong evidence to prove the relationship.
If you had your sample tested for the 25-marker or 37-marker kits, the results will tell you a lot more about your match than the 12-marker test will show. Basically, either or both tests will show the relationships to be much later in time. If you have no matches at the 25-marker or 37-marker levels, you may not find a common ancestor with anyone in our project in the future. However, with time and considerably more participants, you might find a Grant match.
To digress, the comment about finding a matches at the 25 and/or 37 marker levels requires further explanation. Lets suppose you had a perfect match from the 25-marker test. The results would show that you have an 85% probability of a common ancestor within the past 8 generations (about 200 years). And at the 37-marker level, a perfect match would yield an 83% within 4 generations (100 years). The same is true for the 67 and 111 marker test kits.
The table below, which is found on the website in greater detail, provides an overview of all the relevant match combinations: